The present invention relates to apparatus for cutting material in the form of sheets or a web such as are used, for example, in the manufacture of business forms, as well as in the paper, label and folding carton processing industries.
In the paper, label, and folding carton processing industry, webs or sheets of material must often be transversely cut (severed), perforated, or scored. In the integrated business forms industry, patches of transfer tape, release liner and adhesive, plastic laminates, RFID (radio frequency identification) tags, and window materials are often severed from a web and the resulting patches are applied to a continuous web or sheets. In the folding carton industry, windows and other features are often patched onto streams of individual, flattened cartons.
Two methods of rotary cutting such materials are typically employed for these operations: Shear cutting between a rotating blade and a stationary blade, and pressure cutting between a rotating blade and an anvil cylinder.
In rotary shear cutting, a relatively heavy rectangular cutting blade or blades are fastened to corresponding slots in a cutting cylinder with a series of clamping bolts and adjusting screws. The cutting cylinder and blade cooperates with an approximately rectangular stationary blade. The axis of the cutting cylinder may be mounted at a slight angle to the stationary blade, or the rotary blade may be forced into a helical contour so that the material to be cut is severed progressively across its width rather than cut simultaneously. This substantially reduces cutting forces. A precisely adjusted, minuscule gap is maintained between the stationary blade and the moving rotary blade such that a thin material passing between the blades is cut, yet the blades ideally do not physically contact one another. While changing and adjusting rotary shear blades requires more skill and time, rotary shear cutting generally provides longer blade life and a cleaner cut (producing less dust) than rotary pressure cutting.
Rotary shear cutting apparatus lacks the pressure cutting apparatus"" anvil cylinder and so is simpler. However, rotary shear cutting is generally not suitable for cutting materials with adhesive coatings as the adhesive tends to build up on the stationary anvil. Material may then stick to the anvil and cause a jam-up. Further, the anvil is often not easily accessed for cleaning. The rotary blade, however, could be lightly touched to an absorbent roller loaded with silicone fluid once per revolution in order to reduce the tendency of adhesive to stick to the rotary blade. Due to the minuscule gap between rotary and stationary blades, silicon fluid does not readily transfer to the stationary blade and the jamming tendency remains.
In rotary pressure cutting, relatively cheap, thin, flat blades are clamped in a slot or slots in a blade cylinder. The blades are typically clamped with a blade holding bar. The blade cylinder cooperates with an opposing, hardened anvil cylinder. The material to be cut passes between the blade and anvil cylinder. When the blade rotates into the material, the material is pinched between the blade and the anvil surface and sufficient pressure develops to sever the material.
The pressure cutting apparatus may perform alternative functions. In some cases, the height of the cutting blade is adjustable so that the material is not severed, but rather partially cut or scored, or so that one layer of a multi-layer material is selectively cut. Alternatively, a toothed blade may be used to provide perforations, a series of cuts and ties in the material, to provide a line of weakness to assist in subsequent folding or tearing. Further, the anvil cylinder may be provided with a pattern of vacuum holes. While an anvil cylinder with such holes is relatively difficult to manufacture, it allows a patch of material to be severed and conveyed on the surface of the cylinder and applied to another moving material, which may be a continuous web, sheet, carton, object, or a moving belt. Patch or label applicating machines utilize vacuum-equipped anvil cylinders for the manufacture of business forms with integrated labels and cards and other features. Patch applicating machines also use vacuum-equipped anvil cylinders to apply window patches and other features onto blanks that are made into folding cartons.
While versatile and reliable, the rotary pressure cutting method has limitations. High pressures are required to reliably sever typical materials. A rigid, hardened (roughly 62 Rockwell C or more), anvil cylinder is required to resist the repeated, direct contact of a hardened steel blade (roughly 50 Rockwell C or more). Anvil cylinders are manufactured from expensive alloy steels and hardened via careful heat treating procedures. In spite of these costly methods, the repeated, direct contact of the blade causes gradual erosion, or xe2x80x9cscoring,xe2x80x9d of the anvil cylinder""s surface. Cutting of abrasive materials, the use of excessively hard blades, or adjusting blades for excessively hard contact will accelerate damage to the surface of the anvil cylinder. Eventually, the surface of the anvil cylinder will be marked or xe2x80x9cscoredxe2x80x9d deeply enough to inhibit clean, reliable cutting. The anvil cylinder must then be replaced, requiring not only a costly replacement anvil cylinder, but also substantial time to disassemble and reassemble the cutter, with its large frames and bearings and typically heavy cylinders.
In sheeting operations, after a sheet is cut, it is often desirable to control the sheet on rollers or belts. In order to achieve rigidity, the circumference of the anvil cylinder is usually larger than the width of the material being cut. For example, an anvil cylinder for cutting a 20 in. wide paper material may be 24 in. circumference (7.64 in. D). The blade cylinder will typically have similar dimensions. As a result, it is difficult to provide upper and lower rollers or belts to grip or support the sheets much closer than about 3 in. from either side of the cutting point. This limits the shortest piece that may be cut. The relatively long distance from an anvil cylinder to take-away belts or rollers can also cause problems when cutting flimsy or curled materials. Such materials often tend to cling to the anvil cylinder and will not extend from the cutting point sufficiently to smoothly enter the take-away rollers or belts. A scraper blade may act on the anvil cylinder to assist flow of material away from the anvil cylinder, but in practice, scraper blades are typically difficult to adjust and subject to wear. Scraper blades are also susceptible to damage from jam-ups.
Vacuum-equipped anvil cylinders are expensive to manufacture and have additional limitations. One prior art 24 in. circumference, 20 in. wide vacuum cylinder has over 1700 vacuum holes drilled into its hardened surface. Each vacuum hole may be equipped with a metering plug to control the amount of airflow. These vacuum holes communicate with 24 cross-drilled holes that extend through the 20 in. width of the cylinder. The materials, processes, and tooling used in manufacture are expensive.
Vacuum-equipped anvil cylinders experience an important limitation because vacuum holes must be located at predetermined intervals. The 24 in. circumference vacuum cylinder typically has a grid-like pattern of vacuum holes on xc2xd in. circumferential intervals and this does not accommodate some popular business forms repeats. For example, many business forms are printed on a 22 in. circumference press at 3% in., 5xc2xd in., 7⅓ in., 11 in. and 22 in. repeats. The vacuum cylinder with xc2xd in. circumferential vacuum holes will successfully apply patches on 5xc2xd in., 11 in. and 22 in. repeats. However, if one should attempt to cut and apply patches at 3% in. or 7⅓ in. intervals, the blade would regularly cut across a row of vacuum holes and the patch would not be severed. Special gearing kits and blade cylinders have been developed to provide size-specific partial solutions, otherwise a special, costly vacuum cylinder is required with vacuum holes at % in. circumferential spacing.
Flexographic printing presses provide labels and forms on xe2x85x9 in. length increments. To provide windows, adhesive patches, RFID tags and other features on xe2x85x9 in. increments, the size of the vacuum hole must be well under xe2x85x9 in. D. to allow the blade to cut on either side of the vacuum hole. Holes under xe2x85x9 in. D are relatively difficult to drill down to the cross holes and the resulting, long, small diameter hole may cause too much airflow restriction.
When patch applicators are adapted to folder/gluer machines for the folding carton industry, the physical size of the vacuum anvil cylinder may be difficult to accommodate within an existing machine. Further, patch applicators may be servo driven to simplify installation and accommodate positioning inconsistencies of carton blanks on folder/gluer transport belts. The physical size and resulting mass of a vacuum anvil cylinder requires excessively large and expensive servo mechanism drive and control systems (xe2x80x9cservo systemsxe2x80x9d).
The current invention provides a compact, easily replaceable anvil surface for pressure cutting. The anvil surface may be a thin, hardened material supported at the cut region by an opposing support, such as a cylinder, partial cylinder, curved bed or even a flat bed. The addition of an intervening ply of a thin, hard material between a rotary cutting blade and an opposing support provides a compact, low mass anvil surface suitable for cutting, scoring, or perforating. The opposing support may be a hardened cylinder but need not be hard and may be discontinuous. In other words, the anvil surface may be supported by a belt or belts and the belt or belts may be equipped with vacuum holes.
The current invention may be used in conjunction with a conventional vacuum cylinder and overcomes the repeat limitations caused by the need to avoid cutting over a row of vacuum holes.
The invention also allows the elimination of the anvil cylinder with its attendant drawbacks of size, mass, and cost. Eliminating the anvil cylinder also allows closer location of receiving belts or rollers to the cutting point and this permits handling of shorter sheet or patch lengths. This also allows more reliable delivery of sheets of relatively thin, flimsy, non-rigid material into receiving belts or rollers.
Another goal of the invention is to make it easier to add a patch applicator to existing machinery such as printing presses, envelope making machines, and folder/gluer machines for folding cartons. This is accomplished by substituting a vacuum belt assembly in place of a conventional vacuum cylinder. Vacuum belts can more easily extend into an existing machine and transfer patches onto an existing web or stream of sheets, envelopes, or cartons.
Yet another goal of the invention is to provide a lower inertia cutting system that may be more readily servo-driven at lower costs to allow the patching system to deliver accurately located patches onto sheets, envelopes, carton blanks or the like. This is especially advantageous for folder/gluer machines and the like that deliver blanks on relatively inaccurate intervals on transport belts.